Rajendran Muthuraj

What is the solvent and the concentration of the particles? Do you know what the particles are made of? Do you require a particle count by number or a particle size distribution by volume?

you could try dynamic light scattering if the particle concentration is low and you are able to measure the viscosity of the medium

Alan F Rawle

Here is my answer for your questions:

Our solvent is fluorinated solvent and it is highly volatile at RT, the concentration of the particle is

Peter Farrington

I haven't try DLS for our samples, is it possible to use DLS for polymer dissolved in unpleasant solvent like ours. I have contacted few places for DLS analysis but they were denied to analysis our samples because of the solvent. Is there anyway that we can use such a unpleasant solvent system for DLS analysis.

Thanks

Raj

Rajendran Muthuraj Clearly you can use a DLS system with a capped quartz cuvette (assuming your fluorinated solvent doesn't dissolve quartz) and a Peltier to keep the temperature lower than room temperature for the volatility issues you talk about.

Your particle concentration is low (which tends to a counting application). Why do you need a number count?

In the nano-micro range then laser diffraction is likely to be a better bet unless your particles are in proper colloidal suspension. Is there any settling of the particles if you allow the system to stand?

Yes. DLS.

An alternative could also be particle size distribution measurement by acoustic spectrometry: https://www.dispersion.com/product/particle-sizing/

Does anybody have experience with such a device?

Alan F Rawle

Based on your suggestion, I'll try to use DLS and see the outcome.

Thanks for your information.

Cheers

Raj

Pål Baggethun

For me, the acoustic spectrometry is new technique for particle size analysis. I haven't heard about this before. Is it widely available?

Stéphane Bruzaud

Thanks for your reply.

Rajendran Muthuraj Pål Baggethun

Issue with acoustic spectroscopy is its very low resolution. Generally a lognormal 2-parameter model (rather than a model independent) approach is used to obtain a distribution. Concentrations will need to be higher than the 0.3% mentioned earlier. There are a bunch of constants (up to 14) such as the speed of sound in the material to enter. We abandoned the technology after a number of years because of these concerns. In an on-line environment though, changes could be monitored but deconvoluting these changes to PSD changes was extremely difficult.

Rajendran Muthuraj

You still haven't answered my question on why a number count is required or whether settling is observed in the system. DLS will be fine if the concentration is OK and the distribution not too polydisperse and < 1 micron typically. No settling or sedimentation.

Alan F Rawle

The reason behind our interest to get number average is due to the fact that our system is complex and contains number of different particles. Yes the particles could settle if I leave the sample for a long time.

Thanks for your information regarding this question.

Cheers

Raj

Rajendran Muthuraj

If I offered you 2 spherical particles of gold 1 unit and 10 units in diameter, which one would you choose?

Alan F Rawle

I will go with 1

Rajendran Muthuraj If the particles are settling in less than one week then it tells you that the size is in the +1 micron size at least. Carry out a Stokes' Law calculation. DLS is not suited to settling systems usually and this is the region where laser diffraction is a better option, IMHO.

Rajendran Muthuraj

Interesting - you're selecting the smaller particle of 1 unit in diameter when the 10 unit one has a mass of 1000 times (and thus 1000 times the value) of the 1 unit particle. Thank you for leaving me the larger particle.

In a number distribution the 1 and 10 unit particles have equal importance/weighting. In a volume or mass based distribution then the smaller particle can be thrown away as it makes up only 1 part in 1001 of the total mass of the system. See attached.

Alan F Rawle

Thank you for your suggestion, I really appreciated it.

Cheers

Raj

You should use the Dynamic Light Scattering measurements.

@ Seif

Yes, DLS is a good technique for this type of sample and measurements could take place in a quartz cuvette. DLS produces an intensity distribution (i.e. proportional to r6 or volume2).

The poster is saying that he wants a number distribution and DLS does not directly provide this (this conversion is 'deprecated' in ISO22412:2017 and ASTM E2490-09(15))

You can use the zetasizer as equipment for this measurements